FC(F)(F)[C:3]([CH:5]1[CH:10]2[C:11]([CH3:13])([CH3:12])[C:7]([CH3:14])([CH2:8][CH2:9]2)[C:6]1=[O:15])=O.C([O-])([O-])=O.[K+].[K+].C1OCCOCCOCCOCCOCCOC1.C=O>C1C=CC=CC=1>[CH3:12][C:11]1([CH3:13])[C:7]2([CH3:14])[C:6]([C:5](=[CH2:3])[CH:10]1[CH2:9][CH2:8]2)=[O:15]To a solution of 3-(trifluoroacetyl)camphor (45 mg, 0.19 mmol) in benzene (10 mL) were added K2CO3 (82 mg, 0.59 mmol), 18-crown-6 (13 mg, 0.05 mmol), and paraformaldehyde (200 mg, 6.59 mmol). The suspension was heated to 80° C. for 2 h and then heated to reflux (oil bath=90° C.) for 4 h. The mixture was allowed to cool to room temperature, saturated aqueousNH4Cl (10 mL) was added, and the resulting mixture was extracted with EtOAc (3×10 mL). The organics were dried over Na2SO4 and concentrated under reduced pressure. SiO2 flash chromatography (5% Et2O in hexanes) afforded the α-methylene camphor as a pale yellow oil (32 mg) in 95% yield.
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